package com.dcits.util;

import java.io.UnsupportedEncodingException;

public class RSABase64Utils {
		private static char[] base64EncodeChars = new char[]
		{ 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
				'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
				'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5',
				'6', '7', '8', '9', '+', '/' };
		private static byte[] base64DecodeChars = new byte[]
		{ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53,
				54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
				12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29,
				30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1,
				-1, -1, -1 };

		/**
		 * 加密
		 * 
		 * @param data
		 * @return
		 */
		public static String encode(byte[] data)
		{
			StringBuffer sb = new StringBuffer();
			int len = data.length;
			int i = 0;
			int b1, b2, b3;
			while (i < len)
			{
				b1 = data[i++] & 0xff;
				if (i == len)
				{
					sb.append(base64EncodeChars[b1 >>> 2]);
					sb.append(base64EncodeChars[(b1 & 0x3) << 4]);
					sb.append("==");
					break;
				}
				b2 = data[i++] & 0xff;
				if (i == len)
				{
					sb.append(base64EncodeChars[b1 >>> 2]);
					sb.append(base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]);
					sb.append(base64EncodeChars[(b2 & 0x0f) << 2]);
					sb.append("=");
					break;
				}
				b3 = data[i++] & 0xff;
				sb.append(base64EncodeChars[b1 >>> 2]);
				sb.append(base64EncodeChars[((b1 & 0x03) << 4) | ((b2 & 0xf0) >>> 4)]);
				sb.append(base64EncodeChars[((b2 & 0x0f) << 2) | ((b3 & 0xc0) >>> 6)]);
				sb.append(base64EncodeChars[b3 & 0x3f]);
			}
			return sb.toString();
		}

		/**
		 * 解密
		 * 
		 * @param str
		 * @return
		 */
		public static byte[] decode(String str)
		{
			try
			{
				return decodePrivate(str);
			} catch (UnsupportedEncodingException e)
			{
				e.printStackTrace();
			}
			return new byte[]
			{};
		}

		private static byte[] decodePrivate(String str) throws UnsupportedEncodingException
		{
			StringBuffer sb = new StringBuffer();
			byte[] data = null;
			data = str.getBytes("US-ASCII");
			int len = data.length;
			int i = 0;
			int b1, b2, b3, b4;
			while (i < len)
			{

				do
				{
					b1 = base64DecodeChars[data[i++]];
				} while (i < len && b1 == -1);
				if (b1 == -1)
					break;

				do
				{
					b2 = base64DecodeChars[data[i++]];
				} while (i < len && b2 == -1);
				if (b2 == -1)
					break;
				sb.append((char) ((b1 << 2) | ((b2 & 0x30) >>> 4)));

				do
				{
					b3 = data[i++];
					if (b3 == 61)
						return sb.toString().getBytes("iso8859-1");
					b3 = base64DecodeChars[b3];
				} while (i < len && b3 == -1);
				if (b3 == -1)
					break;
				sb.append((char) (((b2 & 0x0f) << 4) | ((b3 & 0x3c) >>> 2)));

				do
				{
					b4 = data[i++];
					if (b4 == 61)
						return sb.toString().getBytes("iso8859-1");
					b4 = base64DecodeChars[b4];
				} while (i < len && b4 == -1);
				if (b4 == -1)
					break;
				sb.append((char) (((b3 & 0x03) << 6) | b4));
			}
			return sb.toString().getBytes("iso8859-1");
		}
}
